Huang Chiu-Jung, Chen Hsing-Yu, Lin Wan-Yi, Choo Kong Bung
Department of Animal Science and 2Graduate Institute of Biotechnology, Chinese Culture University, Yang Ming Shan, Taipei, Taiwan 111.
J Biosci. 2014 Jun;39(3):401-13. doi: 10.1007/s12038-014-9432-1.
The speckle POZ protein, SPOP, is an adaptor of the Cul3-based ubiquitination process, and has been implicated in the carcinogenesis process. Despite recent elucidation of biological functions, regulation of SPOP gene expression has not been reported. In this study, the mRNA levels of the mouse SPOP (mSPOP) gene were first shown to vary noticeably in different tissues. However, the SPOP protein was detected in high abundance only in Purkinje cells of the cerebellum and seminiferous tubule of the testis, echoing previous reports of involvement of ubiquitination in neuron cells and in spermatogenesis. In other mouse tissues and human cancer cell lines analysed, only low SPOP protein levels were detected. The 3'-untranslated regions of both the mSPOP and human SPOP transcripts harbor a conserved putative miR-145 binding site (BS). In some tissues and cell lines, miR-145 and SPOP protein levels were in an inverse relationship suggesting miR-145 regulation. Luciferase assays of deletion and point mutation constructs of the miR-145 BS, and miR-145 induction by serum starvation that resulted in reduced endogenous SPOP levels provided further evidence that miR-145 is likely involved in post-transcriptional regulation of SPOP expression in selected tissues, and possibly with the participation of other miRNA species.
斑点POZ蛋白（SPOP）是基于Cul3的泛素化过程的衔接子，并与致癌过程有关。尽管最近对其生物学功能有了阐明，但尚未报道SPOP基因表达的调控情况。在本研究中，首次发现小鼠SPOP（mSPOP）基因的mRNA水平在不同组织中显著变化。然而，仅在小脑的浦肯野细胞和睾丸的生精小管中检测到高丰度的SPOP蛋白，这与之前关于泛素化参与神经细胞和精子发生的报道一致。在分析的其他小鼠组织和人类癌细胞系中，仅检测到低水平的SPOP蛋白。mSPOP和人类SPOP转录本的3'非翻译区都有一个保守的假定miR-145结合位点（BS）。在一些组织和细胞系中，miR-145和SPOP蛋白水平呈负相关，提示miR-145的调控作用。对miR-145 BS的缺失和点突变构建体进行荧光素酶检测，以及血清饥饿诱导miR-145导致内源性SPOP水平降低，进一步证明miR-145可能参与了特定组织中SPOP表达的转录后调控，并且可能有其他miRNA物种的参与。
